Valve/Piston Clearance

[marcz]

Yep, that's what I was getting at without being alarmist.

Ian... definitely, that is easy and may reveal something provided it isn't what I suspect.

[garym]

This can and does happen||||

[John Johnson]

I had one like that...messy

[LYT4X]

I'm thinking bottom end too.......

You don't have one of those alloy blocks there do you? I very much doubt if a carbon build-up would cause the issue as these things will look a lot worse in close-up on an endoscope than they actually are.

My first suggestion would be a problem at the bottom bearing and next consideration might be a pit of piston slap in #5. The fact that this is prevalent under load suggests much more to do below the level of the cylinder head IMO.

[Julian]

Originally Posted by Ian Simmonds

No, it's more 'load' related, build the rpm slowly and it's only very slightly audible... 'blip' the power and it sounds like a stuck hydraulic tappet on a frosty morning (which, clearly, a WR isn't/hasn't got)...

I agree with the post that follows the one that this quote came from.

Do your ''blipping'' but remove the spark plug leads one at a time - if the noise stops then you've found the knackered bit of bottom end.

(is this the one that you take to 7000revs regularly)

The idea that soot on a piston will cause noise as it hits a valve is not at all likely.

[Ktr]

How long since you looked at the injectors ? if they are weaping they could have diluted the oil causing a problem, just throwing ideas in. Def easier to drop the sump and check the bearings first, clean the oil pick up while your there, only cost you a gasket if nothings wrong

[Ian Simmonds]

Originally Posted by Julian

(is this the one that you take to 7000revs regularly)

Alas, for the general entertainment of the thread, no it's not, it's the standard WR which seldom sees the wrong side of 5k... But hay-ho, would have made everyone laugh wouldn't it...

[Julian]

Originally Posted by Ian Simmonds

Alas, for the general entertainment of the thread, no it's not, it's the standard WR which seldom sees the wrong side of 5k... But hay-ho, would have made everyone laugh wouldn't it...

Ah, but do take note of my serious point. That's the way bottom end noise has been diagnosed and eliminated for decades - no point trying to re-invent the wheel.....